Marvin, Murderous Mimic, Horseshoe Crab, and Incubation Druid

Prerequisites

• Marvin, Murderous Mimic on the battlefield
• Horseshoe Crab on the battlefield
• Incubation Druid on the battlefield
• You control a land that can tap to produce
• Marvin does not have summoning sickness and has at least one +1/+1 counter on it

Steps

1. Activate Marvin using Incubation Druid's ability by tapping it, adding
2. Activate Marvin using Horseshoe Crab's ability by paying , untapping it
3. Repeat

Results

• Infinite mana lands you control can produce